netfilter: conntrack: avoid misleading 'invalid' in log message

The packet is not flagged as invalid: conntrack will accept it and
its associated with the conntrack entry.

This happens e.g. when receiving a retransmitted SYN in SYN_RECV state.
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_conntrack_proto_tcp.c

@@ -982,8 +982,10 @@ int nf_conntrack_tcp_packet(struct nf_conn *ct,
 					IP_CT_EXP_CHALLENGE_ACK;
 		}
 		spin_unlock_bh(&ct->lock);
-		nf_ct_l4proto_log_invalid(skb, ct, "invalid packet ignored in "
-					  "state %s ", tcp_conntrack_names[old_state]);
+		nf_ct_l4proto_log_invalid(skb, ct,
+					  "packet (index %d) in dir %d ignored, state %s",
+					  index, dir,
+					  tcp_conntrack_names[old_state]);
 		return NF_ACCEPT;
 	case TCP_CONNTRACK_MAX:
 		/* Special case for SYN proxy: when the SYN to the server or